Soundness Test

heated · 21-08-2012 6:17pm #1

Just wondered if any of you guys have come accross this problem before?

Carried out a soundness test on an appliance, testing between the appliance isolator valve and gas valve and test failed, but when soundness is carried out at the meter with the appliance isolater valve open, the test passed.

I had this happen on a few different occassions on different makes and models of boiler. Am I missing something or is it simply a faulty isolater valve?

anuprising · 21-08-2012 8:24pm

is there any point in doing a soundness test on the appliance ,if you dont do a let by on the isolator also . this would have given you a difinitive answer on whether the isolator valve was faulty or not . sounds like thats the problem on the various ones you have come across but you really should have checked if you had any doubts about the soundness of an appliance

GASMANN · 21-08-2012 9:02pm

what was the purpose of the test ? just for my own curiosity.

what pressure did you carry out both tests at ?

what were you using to test ?

did you use the same meter for each test ?

[Deleted User] · 21-08-2012 10:27pm

You could of tested from the meter with the appliance off and at the end of the test opened the valve, if it drops when you open the valve then change the valve. The gauge never lies and I wouldn't leave a leak behind me.

(And I'm not trying to score points)

GASMANN · 21-08-2012 10:53pm

that was more or less what i was trying to flesh out gary71, the fact that op is finding the same problem multiple times would make me question the test equipment aswell though.
my reading of it was 2 soundness tests on supply, 1 passed , 1 failed. if the op was testing at standing pressure, 20-25mb, between meter and iso valve, but blowing pressure into the section between valve and appliance ( 1 meter of pipe ? ) could he be testing at 70/80/90mb might a factor.

DGOBS · 21-08-2012 11:42pm

What I assumed has happened here, is the installation was on a med-pressure regulator which is not been correctly soundness tested (hence masked the leak) which was evident on the appliance

At the OP, no this has never happened me, the problem almost certainly lies with the operator, not the installation or equipment!

All questions your been asked about test pressures and procedures are relevant

Please state all test pressures, and test times used, including let-by testing carried out and test equipment used to receive a correct answer, also what type of meter regulator was fitted (low or med pressure reg)

heated · 23-08-2012 12:14am

Thanks for all your replies. Ok first off, This has happened to me on on two different occasions on different boilers. I did carry out a let-by test @ 8-10 mbar before attempting the soundness test and the appliance isolation valve passed let-by test so I proceeded with the soundness test @ 20mbar which failed. I carried out these tests with a u-gauge and then just to check I also carried out the tests with a digital meter and got the same result. Just to be clear, my gauges were connected at the inlet test point on the gas valve. I checked the for leaks between the appliance isolation valve and the gas valve with gas detection fluid and found none so assumed that the seatings on the gas control valve were leaking. I then carried out the same test at the meter (i.e gauge connected on meter test point) with the appliance isolation valve in the closed and the soundness test passed (and yes I first did a let-by test at the meter also) and then with the appliance isolation valve open and to my surprise found that the test passed suggesting that the seatings in the gas valve were ok. As this was not what I expected I re-did all tests and got the same result. Now it's possible I missed something hence my question on here, but as I said I rechecked all tests with two different devices and also tested the isolation valve with gas detecting fluid and found no leak during soundness test. Again just to be clear LP supply in both cases and tests carried out over two minutes after five minutes stabilisation.
Since no leak was present between meter and gas control vlave (i.e appliance Isolation valve open) and no leak was present between meter and the isolated appliance, I am happy the systems were safe, but want to understand why I got the readings I did between the gas control valve and the appliance isolation valve.

[Deleted User] · 23-08-2012 2:32am

U gauge never lies digital can, so trust your u gauge, testing at the meter or the appliance will give the same result. The only thing I would be checking if it was my kit is the gauge rubber hose which can get tiny holes in them and has caught me out before.

[Deleted User] · 23-08-2012 2:34am

GASMANN wrote: »

that was more or less what i was trying to flesh out gary71,

Great minds think a like:D

DGOBS · 23-08-2012 7:29am

Your missing a vital piece of information, what type of regulator was on the gas meter, medium or low pressure?

If it was a medium pressure, and you didn't bleed it off correctly, there may still be up to 4bar (4000mbar) between the MCV and the meter regulator, this pressure essentially is a 'gas supply' and regulator doing what the should, would use this supply to 'replace' any drop in pressure downstream of it.

So if you had a slight leak on the installation side you would not see it for hours!!!

Can you clarify, step by step (exactly) the Letby and soundness test procedure you use at the meter, also if your doing theses tests using gas as your test medium then you are not following the 'new' test procedure as .laid down by RGII, using only air (see latest news letter on the RGII website)

Guys, don't jump on me, I don't think the new procedure is particularly good, or fool proof, but I don't make the rules!

Note to OP, this thread should really be discussed in the RGI tech board, ask Mickey (a mod here for access)

heated · 23-08-2012 9:06am

On a supply with a medium pressure regulator I bleed at the meter until the UPSO drops out on the regulator and then carry out tests. I have queried this before with my own RGII inspector, as it seems to me that the let-by test then in effect becomes a test of the UPSO rather than the ECV, and was told this was acceptable. Sorry didn't realise there was a dedicated RGI discussion board, so will try to access and continue discussion on there.

heated · 23-08-2012 9:17am

@ DGOBS, tried to message Micky but system won't allow me as I don't have enough posts on here.

DGOBS · 23-08-2012 12:02pm

I will message him on your behalf, you will need to supply him with your RGI number etc.

To me, the medium pressure regulator is the key, and my money is on the fact there was excess pressure behind the regulator, in essence masking any leak downstream during your test.

Make sure when you are bleeding off the pressure to letby test, that you hold the hi-limit reset switch (upso) in the middle position to allow the pressure out to 10mbar, if not when the reg locks-up at 14mbar (installation pressure) on the upso it will trap hi pressure behind it (up to 4bar!)

In essence if you look to UK regs (OMG I said the forbidden phrase!!! Gary heeeellpp!!!!!! they are dragging me away......)
you will see that on medium pressure regs you really need to letby test both the MCV and the UPSO, to ensure neither passes,
But the powers that be recon this procedure would just 'confuse' us mere RGI's and our brains would melt!
Then they soundness test at 19mbar (med pressure regs only) to ensure that there is no 'leak masking' pressure still behind the regulator.

This is why we now have the 'air' testing, for both letby and soundness introduced by RGII some months back, to attempt to come up with a 'one fix all from all regulator soundness testing' (flawed as it would seem to be to me!) that doesn't allow you to consider the implications of low pressure regs, medium pressure regs, single stage cylinder regs, two stage bulk tank regs etc.

Go to vipergas, join as a member, and download the booklets, especially the ones concerning soundness and letby testing, it's an enlightening read, and they list sound tried and tested procedures (that you ARE NOT ALLOWED TO USE) for all types of installations.

Sorry for the rant, but this really upsets me, if RGII issued members with a booklet listing the correct procedures for testing these it may reduce accidents due to gas leakage. Not just a procedure using air that someone 'thought up' and assumed it was a good idea!

heated · 23-08-2012 1:06pm

@ DGOBS, thanks for your reply, I will check out the vipergas books straight away. Also thanks for tip on bleeding med pressure reg with reset lever, what about ones with tiny reset button recessed on the back/side?

With the risk of sounding stupid, one thing I'm not clear about is how any pressure trapped on the upstream side of a medium pressure reg would affect a soundness test if the UPSO slam shut is closed and has passed a letby test. Surely the reg cannot work (i.e. regulate the pressure) until the UPSO has been manually reset?

I can certainly see how it might affect a letby test of the ECV if the new RGII test proceedure is followed, (i.e. "On medium pressure distribution systems, after five minutes press the reset button and observe any rise") any trapped pressure would invalidate the letby test of the ECV. However provided it is possible on all types of med pressure regulators in use to reduce the pressure between the ECV and Reg to 10mbar as you suggest, then I guess that takes care of the problem.

DGOBS · 23-08-2012 1:37pm

The reset button on the back side is the same thing, not easy find a mid position, so just keep pressing it in/out until all pressure is released.

Well, it is really the only way/source on your test that could possibly cover the leak on the appliance.
Unless as Gary said earlier, there is an issue with the test equipment.

I agree what your saying about 'until the upso has been reset' but as your working at a test pressure above 14mbar, it possibly could be letting by, have seen some reset themselves when the letby pressure was borderline at operating them.

Just to back track, why were you soundness testing the appliance in the first place, and not the whole installation?

heated · 23-08-2012 2:04pm

No particular reason, I always test the complete installation before I leave, but after working on an appliance particularily If I've had to disconnect the gas valve to get out the burner, I test there first to make sure I've tightened everything up properly and then test the inlet pressure and pressure drop, check the burner pressure (where applicable), then flue gas analysis, before heading out to gas rate and then finally letby and soundness test at meter. Just the routine I follow that's all.

Anyways, Thank for you help, will update you if I ever come across same problem again and figure out what's happening.

anuprising · 23-08-2012 7:37pm

heres what i think is going on .

you arrive at house and test installation from the meter .
proceed to service boiler etc and then soundness test the appliance , with the appliance isolation valve closed . it fails .
you then soundness test from the meter with the appliance isolation valve open and it passes .

when you test the appliance if there is a let by in the appliance isolation valve ,your pressure will drop as it passes back through the valve ,appearing like a leak ,but its just filling the pipe from the meter to the appliance valve ,as you have the pressure dropped in that pipe from the initial test at the meter when you arrived .

disconnect appliance from isolation valve and soundness test from the meter to the isolation valve to confirm let by . change isolation valve

DGOBS · 23-08-2012 10:25pm

If you disconnect, just use some LDF to confirm valve passing

shane0007 · 24-08-2012 12:43am

UK - LPG Let By Test Procedure
1. Connect gauge
2. Turn on gas.
3. Ensure regulator lock up is no more than 52mbar, usually around 39mbar.
4. Turn off gas.
5. Burn off gas to 5mbar.
6. Pull UPSO pin to reset.
7. 5 minutes stabilisation time.
8. 2 minutes test time.

UK LPG Tightness Test Procedure
1. Turn on gas following above let by test.
2. Reset UPSO.
3. All appliance valves on - ensuring cooker lids in upright position.
4. Drop pressure to 30mbar.
5. 5 minutes stabilisation time.
6. 2 minutes test time.

Soundness Test

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